Synthesis And Characterization Of SiC And Rare Earth-doped SiC Nanostructures

Since the successful synthesis of carbon nanotubes, one-dimensional nanomaterials have aroused worldwide attention. Due to its unique electrical, optical and mechanical properties, SiC has thus attracted much interest from many researchers, and become one of the most intensive topics.In this dissertation, the preparations and properties of SiC and Tb-doped SiC optoelectronic nanomaterials were manly studied; moreover, the selective area growth of nanostrucutures were also explored. The main contents including research results of the dissertation are listed as following:(1) SiC and Tb-doped SiC tubular nanomaterials were prepared by using electrospinning technique combining ratio-frequency sputtering method. The nanotubes prepared by our method are straight, smooth and intact. The wall thicknesses of the nanotubes are uniform and controllable, without any impurities. Compared with the film samples, the PL performance of the nantube samples have been obviously enhanced by an order of magnitude. Moreover, the nanotube samples show the excellent FE performance. Based on the above research, the PL performance of Tb-doped SiC nanotubes has been also studied. When the samples were annealed at 900℃through a carbothermal approach, their PL performance have been greatly enhanced. This could due to the decreas of oxygen species within the samples, which result in the decrease of the surface trapping states of the samples.(2) SiC namifibers were synthesized through electrospinning technique combining carbothermal reduction. The SiC nanofibers show a strong blue light emission at 440nm (2.81eV). Based on the above research, the morphologies, structures and PL behaviours of Tb-doped SiC nanofibers were studied. The 1300℃annealed SiC:Tb anno fibers show a thorn-likne morphology, and a strong green light emission that related to Tb3+ ions. Referring to the extended quantum confinement-luminescence center model, a excitation model was proposed to explain the excited energy transfer within our samples. Most of the excited energy comes from the light absorption of the surface SiO2 layer, Tb nanoclusters, and NIRs formed between the SiO2 and SiC cores.(3) SiC hierarchical nanostructures were synthesized by a combining of electrospinning and carbothermal treatment. The as-synthesized samples show excellent PL and FE properties. The growth of SiC nanorods should be governed by the famous VLS mechanism. The preparation process of SiC nanorods contains three steps as following:(a) the formation of Tb nanoclusters, (b) the formation of the catalyst liquid drops, and (c) VLS growth. Incompact nanostructures, necessary pretreatments, satisfactory temperatures, and suitable dopant quantity are should be an organic whole and each aspect is indispensable. Our research may provide new perspectives for selective area growth of SiC nanostructures.